Telephone system



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TELEPHONE SYSTEM Filed Dec. 14, 1925 s Sheets-Sheet e ImrEz-L urs .Eharlss Eflhngs-Jizllzam UgYesbyFassmura .HHF:

. relay in a simp en Patented Dec. 31, 1929 CHARLES GILLINGS AND ASSIGNORS, BY MESNE ASSIGNMENTS, TO

WILLIAM OGLESBY PASSMORE, OF LIVERPOOL, ENGLAND,

AUTOMATIC ELECTRIC INC, OF CHICAGO,

ILLINOIS, A CORPORATION OF DELAWARE TELEPHONE SYSTEM Application filed December 14, 1923, Serial No. 680,636, and in. Great Britain December 19, 192 2.

The present invention concerns improve ments in or relating to telephone systems, more particularly such systems as comprise both manual and automatic exchanges, and the chief object of the invention is to provide diiierent release arrangements according as a connection is extended to an automatic subscriber or to an operator.

According to one feature of the invention, controlling means responsive to adistinctive current transmitted back over a connection are adapted to place the connection under the control of the called party. Preferably this distinctive current is arranged to operate a circuit, i. e. a circuit in which substantially identical current flow over the two talking conductorsinparallel. This relay on operating is adapted to connect guarding potential to the test conductor, in.- dependently of the usual release relay, so that the connection is held up until both the calling and called parties have released. In order to enable the control of the release of a connection to be effected by an operator in a r large multi-ofiice system, the present invention provides special repeating and translating means for meeting the various conditions which arise in such a system.

A further feature of the invention is the provision of a repeater having means responsive to and adapted to retransmit three c is tinctive kinds of current, one consisting of reversals of current over the talking conductors in a two wire circuit, one consisting of ocual currents flowing in the same direction over the talking conductors in a simplex circuit, and the third consisting of pulsating orinterrupted current over one of the talking conductors.

These and other features not specifically mentioned at this point will be better appreciated from the following description taken in conjunction with the accompanying drawings. It will of course be understood that the circuits shown are by way of exampleonly and that considerable detail modification could be made without departing from the spirit of the invention.

Referring now to the drawings, Fig. 1 represents an automatic to automatic repeater 'tablishing at the originating exchange, this repeater be ing accessible from the banks of the local first selectors (not shown). Fig. 2, which is a continuation of Fig. 1, shows an automatic to automatic repeater in atandem exchange, this repeater, being accessible ovier trunk lines and incoming selectors (Fig. 1) and also from the banks of local switches by way of a translating relay. Fig. 3 shows'an automatic to manual repeater for use when the operators position is reached over a two-wire trunk line, while Fig. 4c shows arrangements which can be'used when the operators position is, for instancc, located in the same or and it is considered ad-,

an adjacent building visable to use three wire trunks. Fig. 5 shows an automatic to manual repeater for use when no other repeaters have been used in establishing the connection and Fig. 6 shows the operators position when calls are extended directly thereto, from the banks of local switches. Figs. 7 and 8 are alternative to Figs. 1 and 2 and show an arrangement which, although itinvolves theuse of two controlling relays in the repeater instead of only one, might be preferable in some cases owing to the improved balance obtained. Fi 9 is a diagram showing the general method of esconnections such as will be more fully described hereafter.

The various conditions which may arise will be best appreciated by referring'to Fig. 9. A subscriber at A, of the exchange X may establish connection with an automatic subscriber of exchange X1, over the following route: Substation A, primary line switch C, local first selector D, automatic to automatic repeater R1, trunk line L1, incoming selector D1, connector E, substation A l. Suppose now that the subscriber at substation A wishes to reach operators position 0 in manual exchange X3; the connection will now extend from substation A, line switch C, selector D, repeater R1, trunk line L1, incoming selector D1, automatic to automatic repeater R2, trunk line L2, incoming selector D2, automatic to manual repeater R3, trunk line L3 to operators position 0 in exchange X3. Access may also be obtained to operators position O from substation A1 in exchange X1, by Way of line switch C1 and local selector D3 and thence as before. Access from substation A2 in exchange X2 is obtained by way of line switch C2, selector D 1, repeater R 1 and trunk line L4.

The positions 01 and 02 are manual boards in an automatic exchange X 1 and, being adjacent to the automatic switches, are connected with the local selectors by means of three wire trunks, Connections from substations A and A1 are established to the manual board 01 over repeater R5 and trunk line L5. Connections from the substations A3 to position 02 are completed over the local switches and clearly do not require a repeater. 1

Referring now to Fig. 1 consider first that an automatic subscriber in the first exchange X desires to call an automatic subscriber in the first tandem exchange X1. He will, there fore, remove his receiver and operate his dial in the usual manner thereby controlling the operation of the local first selector with the first digit. The first selector will thereupon seize an idle trunk line leading by way'of a repeater to the required exchange. Suppose that the repeater shown in Fig. 1 is the one selected. As soon as the selector switches through, a circuit is completed over the sub scribers loop, leads 1 and 2 and normally closed contacts controlled by armatures at and 5 for line relay 3. Relay 3 operates, at armature 6 closes a point in the bridge across the outgoing trunk, and at armature 7 con pletes a circuit for slow release relay 8. Relay 8 thereupon energizes, at armature 9 connects earth to release trunk conductor 10, at armature 12 closes a circuit for the polarizing winding of relay 13, and at armature 1d prepares a circuit for slow series relay 15. At armature 11 a circuit is completed as follows :battery, upper winding of the line relay of the incoming selector in exchange X1, upper trunk conductor 16, armature 11 and its Working contact, armature 21 and its resting contact, upper winding of relay 18, upper winding of relay 19, resting con tact and armature 25, armature 22 and its resting contact earth. Relay 18 picks up at once over this circuit and at armature 25 opens the original energizing circuit so that relay 19 is not energized. Furthermore, relay 18, at armature 2 1 short circuits relay 19 by way of armature 39 and its resting contact, and at armature 23 removes the short circuit from the energizing winding of relay 13. A bridge is now completed across the outgoing trunk conductors as follows: from upper trunk conductor 16, armature 11 and its working contact, armature 21 and its resting contact, upper winding of relay 18, working contact and armature 24:, armature 39 and its resting contact, resting contact and armature 33, resting contact and armature 40, lower winding of relay 13 and armature 6 and its Working contact to lower trunk conductor 17. Since however, the flux generated by the current over the lower winding of relay 13 is opposed to that generated by the polarizing upper winding, the said relay does not operate at this time.

The subscriber now proceeds to dial the next digit whereupon line relay 3 is deenergized a plurality of timesin response to the opening of the loop and at armature 6 operates to repeat these impulses over the trunk. On the first deenergization of relay 3 a circuitis completed for series relay 15 by way of armature 7' and its resting contact, armature 14: and its working contact, and armature 32 and its resting contact. Relay 15 thereupon energizes and by virtue of its slow to release characteristic remains energized throughout the train of impulses. On operating, relay 15 at armature 22 opens a further point in the circuit of relay 19, at armature 21 completes a no resistance bridge across the trunk conductors so as to improve 'the impulsing, and at armature 30 opens a point in the metering circuit. A branch of the energizing circuit for relay 15 extends by way of normally closed springs controlled by armature 35 and resting contact and armature 28 to relay 20 which thereupon energizes and at armature 35 locks itself up to the earth on armature 12 and at armature 36 prepares the metering circuit.

The calling subscriber will now dial the remaining digits to extend the connection to the desired line and relay 3 will operate each time to repeat the impulses, relay 15 being energized throughout each train.

When the called man answers, the back bridge relay in the connector will operate to reverse the current back over the connection. the current flow through the lower winding of relay 13 will therefore be reversed, so that this relay now operates. At armature 29 it completes the upper talking conductor independently of armature 21 of relay 15, at armature 26 it completes the lower talking conductor independently of armature 6 of relay 3, at armature 27 it completes a circuit for reversing relay 37, and at armature 23 opens the circuit of relay 20. Relay 37 upon energizing at armatures 4 and 5 reverses the current flow over the subscribers loop according to usual practice and includes additional condensers in the talking circuit and its workingcontact to release trunk conductor 10, so that the calling subscriber's meter. is operated in known manner.

lVhen the conversation is finished, the connection is released under the control of the calling subscriber. When he replaces his receiver, relay 3 deenergizes and after an interval relay 8 also. Thereupon at armature 9 earth is removed from release trunk conduc-tor 10, so that the first selector and the line switch are released. Moreover at armature 11 the loop over the outgoing trunk is opened, so that the operated selectors and connector in the distant exchange are released and all the apparatus used in establishing the connection is restored to normal.

Suppose now that a subscriber in the first exchange X wishes to call a subscriber in the second tandem exchange X2. The call will proceed as before over the repeater R1 but instead of the incoming selector extending the connection over local switches as previously, it will now seize a repeater such as R2 associated with a trunk line to the required exchange. The repeater R2 is'substantially identical with the repeater R1 but has slight modifications to enable it to be seized over local selectors as well as over incoming selectors. For this purpose a relay 53 is provided and instead of a double wound line relay, two separate dine relays 41 and 42 are provided which are connected up over contacts of relay 53 in a manner to be explained more fully subsequently.

In the present instance however the operation of the repeater R2 is precisely similar to that of the repeater R1. WVhen a bridge is closed across conductors and 51 by the operation of the incoming selector, relays 41 and 42 energize, the former completing a circuit for relay 43. Relay 48 puts earth on release trunk conductor 52 to maintain the selector operated and completes a circuit for relay 46 which energizes and comletes a brid 'e across the out 'oin trunk conductors so that the distant selector is prepared for operation in the usual manner. When impulses are transmitted, line relay 41 operates to repeat them over the trunk line and relays 44 and 48 are energized. When the called subscriber replies, current isreversed in the energizing winding of re lay 45, so that this operates and energizes relay 49. This relay therefore also operates and reverses the current back to repeater R1 which thenoperates as previously described. Relays 48 and 49 also jointly initiate a metering operation though clearly in this case it is without effect. The release of the con nection is under the control of the calling subscriber and takes place in a manner which will be apparent from what has gone before.

Suppose now, that the subscriber in the first exchange Xwishes to call a manual operator in a fourth exchange X3 by way of the two tandem exchanges X1 and X2. The operation over two automatic to automatic repeaters, such as R1 and R2 isthe same as has just been described. The incoming selector in the second tandem exchange however, instead of seizing a local switch, seizes an automatic to manualrepeater such as R3, Fig. 3. WVhen the selector switches through a circuit is completed by way of relays 45 and 46 over conductors 100 and 102 for relays 103 and 104. These relays thereupon energize and relay 104 at armature 108 connects earth to release trunk conductor 101 to maintain the preceding selector operated. Relay. 103 at armature 106 connects ring back tone to the upper talking conductor to inform the calling subscriber that the operator is being signalled and at armature 107 completes a circuit for the lower winding of relay 105 and relay 112 in series. It will be noted that as the exchange .X3 is assumed to be a separate manual exchange it has, according to usual practice, a battery of only half the voltage of the battery at the automatic exchange. Consequently a potential difference equal to the difference of voltage between the two batteries is available for energizing relay 112, relay 105 not operating over one winding only. Relay 112 on energizing, at armature 117 lights the calling lamp 113, and at armature 118 places im pedance 116 across the line springs of the jack. When the operator notices the lighted lamp and plugs in, cut oft relay 114 is energized over the jack sleeve and at armature 119 extinguishes the calling lamp and at armature 120 connects relay 115 to the upper talking conductor. Relay 105 is now energized over both windings and accordingly operates. At armature 109 it places a further earth on the release trunk conductor 101 so as to maintain the preceding switches operated when relay 104 momentarily deenergizes, at armature 111 disconnects the ring back tone, thereby notifying the calling subscriber that the operator has answered, and at armature 110 connects battery to the winding of relay 104 instead oi the previous earth. for relay 46 is thereupon broken so that it deenergizes and completes circuits for the upper and lower windings of relay 47 followszbattery, relay 103, upper talking conductor 100, armature 54 and its working contact, armature 59 and its resting con tact, upper winding of relay 46, upper winding of relay 47, resting contact and armature 55, resting contact and armature 56, earth,

battery, armature 110 and its working con-' tact, relay 104, lower talking conductor 102, lower working contact and armature controlled by relay 41, resting contact of armature 58 and said armature, armature 57 and itsresting contact, armature 60 and its rest-- The energizing circuiting contact, lower winding of relay 47, resting contact of armature and said armature, and armature 56 and its resting contact to earth. As soon as relay 47 operates armature 60, which it does very quickly, a new circuit is completed for the lower winding of relay 17 as follows: from battery, armature 110 and its working contact, winding of relay 10 i, lower talking conductor 102, working contact and arn'iature 60, rest ing contact and arn'iature 57, lower winding of relay 46, lower winding of relay 4'? and to earth as before. Relay 17 therefore energizes and at armature 60 and its front contact completes the above described circuit.

Relay 46 does not energize as its windings are traversed by current in opposite direc tions. Relay 47 also at armature 61 connects earth to the mid-point of the winding of relay 78 for a purpose which will appear subsequently, at armature 63 opens the circuit of relay 4%, at armature 64 connects a further earth to the release trunk conductor and at armatures 62 and 65 connects battery to the winding of relay 42 instead of the previous earth connections. This con nection may be traced as follows: earth, battery, armature 62 and its working contact, armature 69 and its resting contact, winding of relay 42, working contact and armature 65, armature 68 and its resting contact and normally closed contacts of relay 49 to lower trunk conductor 51. Hence both the trunk conductors leading to repeater R1 now have battery connected to them so that the same sequence of operations, namely the deenergization of relay 18 and the energization of relay 19, is brought about. The operation of relay 19 performs the same functions as that of relay 47 except that since the repeater R1 is in the originating and not a tandem exchange it is unnecessary to connect battery back over the lower trunk conductor. The relays such as 19 and 47 can be maintained energized over one Winding only, and therefore it is clear that they will be held up until relay 105 deenergizes. As this relay can be held up over one winding only, it is necessary both for the subscriber to hang up and for the operator to remove her plug before the connection can be released, since there is a multiple earth on the release trunk conductor. It will be noted that if the subscriber hangs up first, the upper winding of relays l8 and 46 are disconnected at armatures 11 and 54 and the lower windings are short circuited at armatures 80 and 80 hence these relays do not energize and the circuit through the lower windings of relays 19 and 47 is maintained intact, so that these relays remain energized. It will be noted that when a call is extended to an operator, presumably for complaint or inquiry the current over the speaking leads is not reversed and no metering takes place.

At the same time relay 103 deenergizes and at armature 107 opens the circuit of relay 112 which opens the circuit across the jack springs thus giving the operator a disconnect signal. It will be appreciated that this arrangement of transmitting a disconnect signal without releasing any of the switches is an important feature of the present invention. It will be noted that a subscriber can recall the operator by movinghis switch-hook up and down.

Consider now the establishment of a connection from station A1 to position 0 (Fig. 9) as shown in detail in Figs. 2 and 3. It is supposed that a connection is extended from the calling substation over a local selector to the line comprising conductors 72. As soon as the selector switches through, a circuit is completed for relays 41 and 4-2 as follows: battery, winding of relay 41, normally closed contacts controlled by relay 49, lead 71, subscribers loop, lead 70, normally closed contacts controlled by relay 4&9, normally closed contacts controlled by armature 62, resting contact and armature 69, winding of relay 4L2, normally closed contacts controlled by armature 65, earth. Relays 4:1 and -12 therefore operate, complete the circuit for release relay 43 and prepare the repeater for operation in the usual manner. Among other operations, relay 43 puts earth on release trunk conductor 72. As soon as the release relay in the local selector deenergizes, the current for maintaining the switching relays of the selector and line switch operated will flow from earth at armature 73 over the very low resistance upper Winding of relay 53. This relay therefore picks up, at armature 66 short circuits its upper winding, at armature 67 locks itself to the release trunk conductor by way of its lower winding, and at armatures 68 and 69 prepares an alternative circuit for relay a2. dial the remaining digits and the operation of extending the connection to the operators position (Fig. 3) takes place as just described.

lVhen the operator plugs in, relay 105 is energized and accordingly relay 47. It will be appreciated that in this case when relay 47 operates, battery is not connected to the lower talking conductor owing to the operation of translating relay 53. Obviously this battery connection would be highly undesirable since there would then be no feeding current for the transmitter at the callingsubstation. The release of the connection is again brought about when the subscriber hangs up or when the operator withdraws her plug, whichever happens last.

It will now be assumed that the subscriber at substation A2 wishes to extend a call to the operators position at 0 (Fig. 9); this.

The calling subscriber will noW' can be traced in detail with the help of Fig. 5. It is assumed that the automatic to man ual repeater R4 is seized by way of a primary line svitch and a local first selector in the usual manner. When the loop is completed at the selector across conductors 121 and 122, relay 124 is energized. On operating relay 124 at arn'iature 126 puts earth on release trunk conductor 123 to maintain the selector and line switch operated, at armature 127 connects up ring back tone to notify the calling subscriber that'the operator is being signalled and at armature 128 completes a circuit for relay 131 and the lower winding of relay 125 in series. Relay 131 alone operates and at armature 137 lights the'calling lamp 135 and at armature 136 places impedance 132 across the line springs of the ack. When the operator plugs in in response to the lighting of lamp 135, out off relay 133 is energized over the sleeve of the plug, at armature 138 extinguishes the calling lamp and at armature 139 completes a circuit for relay 134 and'the upper winding of relay 125 in series. Relay 125 now operates over both its windings, at armature 130 disconnects the ring back-tone to indicate the operators reply and at armature 129 puts a multiple earth on the release trunk. Clearly inthis case also the release takes place when both the operator has withdrawn-her plug and the calling subscriber has replaced his receiver.

Consider now thetracing of a connection from the automatic subscriber at A1 to an operators position 01 (Fig. 9) which is assumed to be reached by way oi": repeater R and by'three wire trunks from the local selectors. This connection can be followed in detail withthe help of Figs. 2 and 4.

The progress of the connection from the local selectorover relay'53, repeater R ,'incoming selector, similar repeater R and corresponding incoming selector is again as previously described. When the bridge is completed across conductors 140 and 141 of the three wire trunk, relay 1 43 is energizedby way of armature 155 and its resting contact. On operating relay 143 at armature 148 connects ring back tone to the line, at armature 149 completes circuits for slow relay 144 and calling lamp 151 and at armature 150 connects impedance 146 across the line springs of the jack. Relay 144 upon energizing, places earth on release trunk conductor 142 at armature 152 so as to hold the preceding switches operated. When the operator plugs in, cut off relay 147 is energized, at armature 156 can tinguishes the calling lamp, at armature 154 prepares a parallel earth connection to the release trunk conductor and at armature 155 cuts out the lower winding of relay 143 and substitutes the winding of relay 145; relay 143, however, is maintained energizedover its upper winding alone. Relay 145 energizes to disconnect ring back tone at armature 153.

The relay in repeater R corresponding to relay 47 in repeater R is energized over the usual simplex circuit and operates in the manner previously described to repeat the characteristic current to repeater R It will be seen that if the subscriber hangs up before the operator takes out her plug, earth will be maintained on the release trunk by way of armature 154 and the connection will be accordingly held up. 7

Still another case has to be considered, namely the sequence of operations when the subscriber at A (Fig. 9) wishes to call the operator at position O2, this connection being entirely local so that three wire trunks are employed. The operators position is shown in Fig. 6. Again it is assumed that access is obtained over the usual line switch and first selector.

When the selector switches through a circuit is completed as follows: battery, winding of line relay 160, armature 167 and its resting contact, upper talking conductor 157, subscribers loop, lower talking conductor 158, resting contact and armature 168, earth. Relay 160 energizes in this circuit, at armature 163 lights the calling lamp 162, at armature 164 connects ring back tone to the line, and at armature 165 puts earth on release trunk conductor 159. When the operator plugs in in response to the lighting of the lamp 162, out 011? relay 161 is energized and at armatures 167 and 168 disconnects the line relay, at the former armature also disconnecting the ring back tone, and at armature 166 puts a further earth on release trunk 159. Relay 160 is made slightly slow to insure that earth will come on at armature 166 before it is taken ofi' at armature 165. It will readily be seen that the release of the connection is now under the joint control of the operator and the subscriber as in the previous cases. A further function of the relays such as 19 and 47 which has not yet been described is that of repeating the busy signal. It is arranged that when the wipers of a selector are moved to the eleventh contact owing to all Y connected to the mid point of the winding of the busy flash relay 78. Relay 78 is then partially operated so as to make-armature 7 4 engage its working contact, earth being then connected to the other end of the winding of relay 78 by way of armature 79. When the busy tone comes on instead of busy flash battery, relay 47 is again deenergized and takes earth off the mid point of relay 78 so that as its upper winding is no longer short circuited it now operates fully. At armature 75 it looks itself up by permanently removing earth from the mid point of its winding, and at armatures 7 6 and 7'? connects up busy flash battery and busy tone from a local source alternately to the lower talking conductor leading to the preceding switch. If the call originated at an automatic substation, the subscriber will hear the busy tone in his receiver in the usual way; if, however, the call was set up from an operators position, she will be notified by the flashing of the supervisory lamp which will be operated by the busy flash battery.

A brief description of the modifications shown in Figs. 7 and 8 will now be given. It will be seen that the chief difference in volved is that instead of the single relays such as 19 or 4 pairs of relays are now employed.

In Fig. 7 when the line and release relays have operated in response to the seizure of the r peater, a bridge across the trunk conductors 200 and 201 is closed as follows conductor 200, armature 206 and its working contact, armature 207 and its resting contact, armature 208 and its resting contact, upper winding of relay 203, resting contact anl armature 209, lower winding of relay 202, armature 210 and its working contact, conductor 201. Relay 203 therefore energizes in series with the line relay of the incoming selector, but relay 202 does not energize with current in this direction. circuit is also momentarily completed from the winding of relay 202, winding of relay 205, armature 211 and its resting contact, armature 212 and its resting contact, earth. As, however, this circuit immediately opened at armature 211, relay 205 does not energize at this time. The transmission of impulses now takes place in the usual way. If owing to an operator plugging in at the distant end of the connection, the connection of battery to the lower trunk conductor is relayed back to the repeater in Fig. 7, relay 203 is deenergized. As soon as armature 211 err gages with its resting contact, a circuit will be completed for relay 205. On energizing, relay 205 at armature 213 connects an additional earth to the release trunk conductor, at arms. ture 21 1- shunts repeating contact 210 of the line relay, at armature 215 connects up the busy flash relay and at armature disconnects relays 202 and 203 and substitutes relay 204;. Clearly both these relays 204. and 205 will remain energized until the operator removes her plug, unless the subscriber hangs up first. In this'case relay 20 1 will. deenergize but the connection will still be held up owing to the earth on the release trunk conductor at armature 213.

The operation of the repeater shown in Fig. 8 is substantially identical though of course modified by the translating relay and A branch of this the two line relaysfand by the fact that it is adapted to relay back the connection of battery to the lower trunk. In view therefore of Figs. 2 and 7 no detailed description of the operation of the repeater in Fig. 8 will be given.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be per formed, we declare that what we claim is:

1. In a telephone system, a first automatic switch, an automatic repeater, a second automatic switch, a manual switchboard, a trunk line having two talking conductors extending to said switchboard, means including said first automatic switch for extending a conn ction to said repeater, said repeater including means for repeating a train of impulses to said second automatic switch to extend a connection to said switchboard, a battery at said switchboard having one terminal connected to one conductor of said trunk line and having the other terminal connected to the other conductor thereof, means rendered effective by the response of the operator at said switchboard to disconnect one of the conductors of said connection from the associated terminal of said battery and to connect it instead to the other terminal of said battery, and means in said repeater responsive to this operation to close a holding circuit for the said first automatic switch.

2. In a telephone system, a first automatic switch, an automatic repeater, a second automatic switch, a manual switchboard, a trunk line having two talking conductors extending to said switchboard, means includlng said first automatic switch for extendlng a connection to said repeater, said repeater including means for repeating a train of impulses to said second automatic switch to extend a connection to said switchboard, a battery at said switchboard having one terminal connected to one conductor of said trunk line and having the other terminal connected to the other conductor thereof, means rendered effective by the response of the operator at said switchboard to disconnect one of the conductors of said connection from the associated terminal of said battery and to connect it instead to the other terminal of said battery, and means in said repeater responsive to this operation for placing the holding of the first switch under the control of the operator.

3. In a telephone system, a first automatic switch, an automatic repeater, a second automatic switch, a manual switchboard, a trunk line having two talking conductors extending to said switchboard, means including said first automatic switch for extending a connection to said repeater, said repeater including means for repeating a train of impulses to said second automatic switch to extend a connection to said switchboard, a battery at said switchboard having one terminal connected to one conductor of said' trunk line and having the other terminal connected to the other conductor thereof, means rendered effective by the response of the operator at said switchboard to disconnectone of the conductors of said connection from the associated terminal of said battery and to connect it instead to the other terminal of said battery, and means in said repeater responsive to this operation for placing the holding of the first switch under the oint control of the operator and the calling party.

4. In a telephone system, a first automatic switch, a second automatic switch, a trunk line extending from the bank of the first automatic switch to said second automatic switch, an automatic repeater in said trunk line, means for operating said first automatic switch to extend a connection to said repeater, means in said repeater controlled over said connection for closing a holding circuit for said first automatic switch and for closing a control circuit for said second automatic switch including the two conductors of said trunk line in series, means for controlling said repeater over said connection to repeat impulses to operate said second automatic switch, a manual switchboard, a trunk line terminating at one end in said manual switchboard, means including said second automatic switch when so operated for extending a connection to said switchboard by way of the associated trunk line, abattery having its two terminals connected to the respective talking conductors of the last said trunk line, and means controlled by the response of the operator atsaid switchboard for disconnecting one of the conductors of said trunk line from the associated terminal of said battery and for connecting it to the other terminal or" said battery, and means in said repeater responsive to this operation for closing a holding circuit for said first automatic switch independent of the control over said connection.

5. In a telephone system, a first automatic switch, a first repeater, a trunk line extending from said repeater to a second automatic switch, a second repeater, a trunk line extending from said second repeater to a third automatic'switch, a trunk line extending to a manal switchboard, means for operating said first switch, to extend a connection to said second switch by way of said first repeater and the associated trunk line, means in said first repeater for repeating impulses over the associated trunk line to operate said second switch to extend a connection to said third switch by way of said second repeater and the associated trunk line, means in the second repeater for repeating impulses to said third switch for operating said third switch to extend a connection to said manual switchboard over the associated trunk line, means operated upon the response of the operator at the manual switchboard for placing a holding condition on the associated trunk line, means in the second repeater responsive to this operation for holding the second automatic switch operated and for placing a holding condition on the associated trunk line, and means in the first repeater responsive to this operation for holding said first automatic switch operated.

6. In a telephone system, a first repeater, a first trunk line extending to said repeater, a second trunk line extending from said repeater to a distant automatic switch, means including a second repeater and an incoming automatic switch for extending a connection over the first trunk line to said first repeater, other means including a local automatic switch for extending a connection over said trunk line to said distant switch, a manual switchboard, a trunk line leading to said switchboard, means in said repeater operative when the repeater is seized by said incoming switch or by said local switch to repeat impulses to operate said distant switch to extend a connection to said manual switchboard over the said associated trunk line, means rendered effective by the response of the operator at said switchboard for placing a holding condition on the associated trunk line, and means in said automatic repeater responsive to this operation for holding the seizing switch operated and for placing a holding condition on said first trunk line or not depending upon whether the said first repeater was seized by the said incoming switch or by the said local switch.

7. In a telephone system, a repeater for repeating impulses in one direction including means responsive to three distinctive kinds of current to retransmit such currents in the other direction, one kind consisting of reversals of current over the talking conductors in series, one consisting of equal currents flowings over the talking conductors in parallel, and the third consisting of intermittent current flow over one of the talking conductors alone.

8. In a telephone system, an automatic repeater, an automatic switch, a trunk line ex tending from said repeater to said switch, a manual switchboard, a second trunk line extending to said switchboard, means in said automatic repeater for repeating a series of impulses over the associated trunk line to operate said automatic switch to extend a connection over said second trunk line to said switchoard, means at said switchboard for placing holding condition on said second trunk line, a holding conductor at said repeater, and means responsive to the said holding condition for placing a holding potential on said holding conductor.

9. In a telephone system, means including an automatic switch, an impulse repeater, a two-conductor trunk line, a second automatic switch, and a second two-conductor trunk ill) line for extending a connection to a manual switchboard, means controlled at said switchboard for placing a holding condition on said second trunk l ne, means in said repeater rcsponsive to this holding condition for clos ing a holding circuit for the first named automatic sivitch, means under the control of the calling party for signalling the operator by stopping the current fiow over one talking conductor of the established connection, said means in the repeater for holding the first switch operated being maintained operated over the other talking conductor.

10. In a telephone system, a repeater for repeating impulses in one direction, and relays in said repeater responsive to three ditierent kinds of current to repeat such currents in the other direction.

11. In a telephone system, a repeater, a first-trunk extending to said repeater and a second trunk extending from said repeater, means in said repeater for repeating impulses to said second trunk, and means in said repeater for reversing the flow of current over the talking conductors of said first trunk, for connecting equal sources of potential to the talking conductors of said first trunk in parallel, and for causing an intermittent fiow of current over only one of the talking conductors of said first trunk.

12. In telephone system, a plurality of automatic switches, an impulse repeating repeater, means controlled by a calling subscriber for operating said switches to connect with said repeater and for causing said repeater to repeat impulses to operate other automatic switches to complete a connection with either a called subscriber or an opera-i tors position, the release out said switches being normally controlled by the calling subscriber, and means in said repeater for enabling the operator to control the releasing oi said switches when a connection is completed with an operators position.

13, In a telephone system, a trunk line extending to an operators position, means ineluding two repeaters and a plurality of switches for extending a connection from a calling subseribers line to said trunk line, the established connection including one or more of said switches between the calling line and the first repeater and one or more switches between said repeaters, means at said position for altering the electrical condition of said trunk line, means in the second repeater responsive to such alteration for preventing the release of the switches between the repeaters and also for repeating the altered circuit condition into the trunk circuit extending back to the first repeater, and means in the first repeater responsive to such altered condition for preventing the release of the switches between the first repeater and the calling line.

14. In a telephone system, a repeater, a

two conductor trunk outgoing from said repeater, a relay in said repeater, an energizing circuit for said relay including only one conductor of said trunk and a ground return, means for closing said circuit as soon as the repeater is seized to energize said relay, and means controlled by the operation of said relay for altering said circuit so that the same includes both conductors of said trunk.

15. In a telephone system, a repeater, a two conductor trunk associated with said repeater, a first and a second relay in said repeater, an energizing circuit for said first relay including only one conductor of said trunk and a winding of said second relay and a ground return, means for closing said circuit as soon as the repeater is seized to energize said first relay, and means controlled by the operation of said first relay for opening said circuit, for substituting a holding circuit therefore, and for short circuiting said second relay.

16. In a telephone system a repeater, a two conductor trunk associated with said repeater, a first and a second relay in said repe ter, an energizing circuit for said first relay including only one conductor of said trunk and winding of said second relay and a ground return, means for closing said circuit as soon the repeater is seized to energize said first relay. means controlled by the operation of said first relay for opening said circuit, for substituting a holding circuit therefore, and for short circuiting said second relay, an operators position, means controlled by the operator at said position for deenergizing said first relay, and means controlled by the deenergization of said first relay for closing a circuit to energize said second relay.

17. In a telephone system, a repeater, a two conductor trunk associated with said repeater, a first and a second relay in said repeater, an energizing circuit for said first relay including only one conductor of said trunk and a winding of said second relay and a ground return, means for closing said circuit as soon as the repeater is seized to energize said first relay, means controlled by the operation of said first relay for openin said circuitior substituting a holding circuit therefore, and for short circuiting said. second relay, an operators position, means controlled by the operator at said position for deenergizing said first relay, means controlled by the deenergization of said first relay for closing a circuit to energize said second relay, and means controlled by said second relay for closing a holding circuit for itself which is controlled over the said other conductor.

18. In a telephone system, a repeater, a two conductor trunk associated with said repeater, a first and a second relay in said repeater, an energizing circuit for said first relay including only one conductor of said trunk and winding of said second relay and a ground return, means for closing said circuit as soon as the repeater is seized to energize said first relay, means controlled by the operation of said first relay for opening said circuit, for substituting a holding circuit therefore, and for short circuiting said second relay, and means responsive to an encountered busy condition for deenergizing said first relay and for energizing said second relay.

19. In a telephone system, a repeater, a two conductor trunk associated with said repeater,

a first and a second relay in said repeater, an energizing circuit for said first relay including only one conductor of said trunk and a winding of said second relay and a ground return, means for closing said circuit as soon as the repeater is seized to energize said first relay, means controlled by the operation of said first relay for opening said circuit, for substituting a holding circuit therefore, and for short circuiting said second relay, means responsive to an encountered busy condition for deenergizing said first relay and for energizing said second relay, and means responsive to the operation of said second relay for connecting a busy tone to the other conductor.

20. In a telephone system, means including a plurality of trunk lines and a plurality of repeaters for extending a connection, a separate source of busy current at each of said repeaters, and means responsive to an 'encountered busy condition in extending said connection for connecting up said sources of busy current at each of said repeaters.

21. In a telephone system, means including two repeaters and a plurality of switches for extending a connection from a calling line, the established connection including one or more of said switches between said repeaters, a separate source of busy current at each of said repeaters, and means responsive to an encountered busy condition in extending said connection for connecting up said sources of busy current at each of said repeaters.

22. In a telephone system, means including two repeaters and a plurality of switches for extending a connection from a calling line, the established connection including one or more of said switches between said repeaters, a separate source of busy current at each of said repeaters, means responsive to an encountered busy condition in extending said connection for connecting up the source of busy current at the second of said repeaters, and means in the first of said repeaters responsive to the connected busy source at said second repeater for connecting up the source of busy current at the first of said repeaters.

23. In a telephone system, means including two repeaters and a plurality of switches for extending a connection from a calling line, a busy flash source of current at the second of said repeaters, a busy tone source at the first of said repeaters, means in said second repeater responsive to one of said switches encountering a busy condition in extending said connection for connecting up said busy flash source to said second repeater, and means in said first repeater responsive to the connection of said busy flash source to said second repeater for connecting up said busy tone source at said first repeater to said first repeater in order to transmit a busy tone to the calling subscriber.

24. In a telephone system, means including two repeaters and a plurality of switches for extending a connection from a calling line, a busy flash source of current and a busy tone source of current at each of said repeaters, means in the second of said repeaters responsive to one of said switches encountering a busy condition in extending said connection for connecting up said busy flash source and said busy tone source to said second repeater, and means in the first of said repeaters responsive to the connection of said sources at said second repeater for connecting up said busy flash source and said busy tone source at said first repeater to said first repeater.

25. In a telephone system, an operators position, means including two repeaters and a plurality of switches for extending a connection from a calling line to said position, a busy flash source of current and a busy tone source of current at each of said repeaters, operator controlled means at said position for connecting a busy flash source to said connection at said position when the desired called line is busy, means in the second of said repeaters responsive to the connection of the busy flash source at said position for connecting up said busy flash source and said busy tone source at said second repeater, and means in the first of said repeaters responsive to the connection of said sources at said second repeater for connecting up said busy flash source and said busy tone source at said first repeater to said first repeater.

26. In a telephone system, an automatic repeater, a first trunk line extending to said repeater, a second trunk line extending from said repeater to an automatic switch, means in said repeater for repeating impulses to operate said switch to extend the connection, means for intermittently applying a potential to one conductor only of said second trunk line responsive to said switch encountering a busy condition, and means in said repeater operated responsive to said intermittent applications of potential for repeating such applications to one conductor only of the first trunk line.

Signed by me at Liverpool, England, this 12th day of November, 1923.

CHARLES GILLINGS.

Signed by me at Liverpool, England, this 12th day of November, 1923.

WILLIAM OGLESBY PASSMORE. 

